Exhaust silencer with acoustic damping mat

ABSTRACT

An exhaust silencer includes an upper shell and a lower shell attached to the upper shell to define an internal cavity. Acoustic damping material is positioned within said internal cavity to reduce radiated and transmitted noise. A plurality of retention members compresses the acoustic damping material against an inner surface of the upper shell. The acoustic damping material is only located in the upper shell and thus is not affected by condensate that collects in the lower shell.

TECHNICAL FIELD

The subject invention relates to an exhaust silencer that includes acoustic damping material to reduce noise.

BACKGROUND OF THE INVENTION

An exhaust silencer includes an upper shell and a lower shell that together define an internal cavity. Baffle holes and extrusions are formed within the internal cavity. Exhaust air flows from an inlet, through the baffle holes and extrusions, and out an outlet. The baffle holes and extrusions define an exhaust flow path and cooperate to reduce noise as exhaust air flows through the exhaust silencer.

Some disadvantages with this traditional exhaust silencer configuration are mid-frequency noise attenuation capability and shell resonance noise. One solution that has been used to address these noise issues has been to provide an exhaust silencer that is loosely filled with acoustic damping material. This solution has provided unsatisfactory results. In this configuration, loose fill falls into the exhaust flow path, which can increase back-pressure. Further, the loose fill settles into the lower shell where condensate typically collects. Thus, the loose fill soaks up the condensate, which can degrade the loose fill and also can prevent the condensate from draining out of the lower shell as needed.

Thus, there is a need for an exhaust silencer that can reduce radiated as well as transmitted noise without increasing back pressure and adversely affecting operation of the exhaust silencer.

SUMMARY OF THE INVENTION

An exhaust silencer includes an upper shell and a lower shell attached to the upper shell to define an internal cavity. Acoustic damping material is compressed against an inner surface of the upper shell to reduce radiated and transmitted noise. The acoustic damping material is only located in the upper shell and thus is not affected by condensate that collects within the lower shell during vehicle operation.

The exhaust silencer includes at least one retention member that provides and maintains a compression force against the acoustic damping material. In one example, the at least one retention member includes a plurality of straps. Each of the plurality of straps has a center portion that extends between first and second strap ends. The center portion engages and compresses the acoustic damping material against the upper shell, with the first and second strap ends directly mounted to the upper shell.

Locating the acoustic damping material only in the upper shell keeps the acoustic damping material dry and avoids placing the acoustic damping material in an exhaust flow path through the exhaust silencer. Also, shell resonance for both the upper and lower shells is improved. These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembled perspective view of an exhaust silencer incorporating the subject invention.

FIG. 2 is side cross-sectional view of the exhaust silencer of FIG. 1.

FIG. 3 is an end cross-sectional view of the exhaust silencer of FIG. 2.

FIG. 4 is a perspective view of one example of a side retention member.

FIG. 5 is a perspective view of one example of a bottom retention member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An exhaust silencer 10 is shown in FIG. 1 and includes in inlet 12 and an outlet 14. The inlet 12 is in communication with an upstream exhaust system component and the outlet 14 is in communication with a downstream exhaust system component as known.

The exhaust silencer 10 includes an upper shell 16 that is attached to a lower shell 18 to define an internal cavity 20, see FIG. 2. Baffle holes and extrusions are located within the internal cavity 20 as known, but are not shown for reasons of clarity. Exhaust air flows along a flow path extending from the inlet 12, through the baffle holes and extrusions, and out the outlet 14.

Acoustic damping material 22 is pressed against an inner surface 24 of the upper shell 16. The acoustic damping material 22 reduces transmitted noise generated by exhaust flow and reduces radiated noise generated by resonance of the upper 16 and lower 18 shells.

In the example shown in FIG. 2, the acoustic damping material 22 is formed as a mat 26 that covers a first portion 30 of the inner surface 24 of the upper shell 16. A second portion 32 of the inner surface 24 of the upper shell 16 remains uncovered, i.e. the second portion 32 is not covered by acoustic damping material 22. The amount of coverage of the first portion 30 relative to the second portion 32 can vary depending upon vehicle application, size, and/or other known specifications. A smaller mat portion, when maintained in compression against the upper shell 16, can act as a mute for both the upper 16 and lower 18 shell. A larger mat portion additionally increases attenuation of high frequency aural content by diffusing, absorbing, and scattering short-length sound waves.

The mat 26 is only located within the upper shell 16. By physically locating the mat 26 only in the upper shell 16, the acoustic damping material 22 is kept dry. This allows condensate, which typically collects in the lower shell 18 to be properly drained from the lower shell. Further, by pressing the mat 26 against the inner surface 24 of the upper shell 16, the acoustic damping material 22 is not located in the flow path of the exhaust air.

At least one retention member 40 is used to provide and maintain a compression force against the mat 26. In one example, shown in FIGS. 2 and 3, the at least one retention member 40 comprises a plurality of retention members 40. In the example shown, each retention member 40 is a strap having a center portion 42 that extends between first 44 and second 46 strap ends. The center portion 42 compresses the mat 26 against the inner surface 24 of the upper shell 16. The first 44 and second 46 strap ends extend beyond the mat 26 and are directly attached to the upper shell 16. The first 44 and second 46 strap ends are preferably puddle welded to the upper shell 16, however, other attachment methods could also be used.

As shown in FIG. 3, the upper shell 16 includes an upper wall 50 and a pair of vertical side walls 52 extending from opposing edges of the upper wall 50. In one configuration, the plurality of retention members 40 includes a first strap 54 fixed to one of the pair of vertical side walls 52 and a second strap 56 fixed to another of the pair of vertical side walls 52. A third strap 58 is fixed to the upper wall 50 adjacent one of the opposing edges and a fourth strap 60 is fixed to the upper wall 50 adjacent another of the opposing edges. The first 54, second 56, third 58, and fourth 60 straps cooperate to securely hold and maintain the mat 26 in compression against the upper shell 16.

FIG. 4 shows one example of a strap configuration that could be used for either the first 54 or second 56 strap. This strap configuration provides a strap body 62 with transversely extending first 64 and second 66 strap ends. The strap body 62 includes rib portions 68 that generally correspond in shape to ribs 70 formed on the upper shell 16 (see FIG. 1). The mat 26 is compressed between one vertical side wall 52 and the strap body 62 and the first 64 and second 66 strap ends are attached to the upper shell 16 as described above.

FIG. 5 shows one example of a strap configuration that could be used for either the third 58 or fourth 60 strap. This strap configuration provides a strap body 72 with transversely extending first 74 and second 76 strap ends. The strap body 72 is curved to match a curved profile 78 of the upper shell 16 (see FIG. 1). The strap body 72 includes rib portions 80 that generally correspond in shape to the ribs 70 on the upper shell 16. The mat 26 is compressed between the upper wall 50 and the strap body 72 and the first 74 and second 76 strap ends are attached to the upper shell 16 as described above.

Any type of acoustic damping material 22 known in the art can be used to form the mat 26. In one example, an E-glass silentex powertex material manufactured by BGF Industries is used to form the mat, however, other fiberglass materials, or other materials, could also be used. Additionally, the upper 16 and lower 18 shells, and the straps shown in FIGS. 4 and 5 are preferably made from 409 stainless steel, however, other known materials could also be used.

It should be understood that straps are just one example of a retention member that could be used to compress the mat 26 against the upper shell 16. Bands, baffles, netting or an inner shell portion could also be used to hold the mat 26 in place.

As discussed above, the subject invention provides an exhaust silencer 10 with improved acoustic damping. Locating the acoustic damping material 22 only in the upper shell 16 keeps the acoustic damping material 22 dry and avoids placing the acoustic damping material 22 in an exhaust flow path through the exhaust silencer 10. Also, shell resonance for both the upper 16 and lower 18 shells is improved.

Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention. 

1. An exhaust silencer comprising: an upper shell; a lower shell attached to said upper shell to define an internal cavity; and acoustic damping material held within said internal cavity against said upper shell.
 2. The exhaust silencer according to claim 1 wherein said acoustic damping material is compressed against an inner surface of said upper shell.
 3. The exhaust silencer according to claim 2 wherein said acoustic damping material comprises a mat having a first surface substantially engaging said inner surface and a second surface facing said internal cavity.
 4. The exhaust silencer according to claim 3 including at least one compression member in engagement with said second surface to generate a retaining force for holding said mat against said upper shell.
 5. The exhaust silencer according to claim 4 wherein said at least one compression member comprises a plurality of straps.
 6. The exhaust silencer according to claim 5 wherein each of said plurality of straps has a pair of strap ends interconnected by a center portion wherein said center portion engages said mat with each of said pair of strap ends being directly attached to said upper shell.
 7. The exhaust silencer according to claim 3 wherein said inner surface of said upper shell has a first portion and a second portion wherein said first portion is uncovered and said second portion is covered with said mat.
 8. The exhaust silencer according to claim 1 wherein said acoustic damping material is only located in said upper shell.
 9. The exhaust silencer according to claim 8 including an inlet to be in communication with a first exhaust system component and an outlet to be in communication with a second exhaust system component wherein said acoustic damping material reduces radiated and transmitted noise as exhaust air moves through said internal cavity from said inlet to said outlet.
 10. The exhaust silencer according to claim 8 wherein said acoustic damping material includes fiberglass material.
 11. An exhaust silencer comprising: an upper shell; a lower shell attached to said upper shell to define an internal cavity; acoustic damping material positioned within said internal cavity; and a plurality of retention members compressing said acoustic damping material against an inner surface of said upper shell.
 12. The exhaust silencer according to claim 11 wherein said lower shell provides an uncovered inner surface spaced apart from said acoustic damping material.
 13. The exhaust silencer according to claim 11 wherein said acoustic damping material is only located in said upper shell.
 14. The exhaust silencer according to claim 13 wherein said plurality of retention members comprises a plurality of straps with each of said plurality of straps having a center portion interconnecting a pair of strap ends, said center portion engaging said acoustic damping material with each of said pair of strap ends being directly attached to said upper shell.
 15. The exhaust silencer according to claim 14 wherein each end of said pair of strap ends is welded to said upper shell.
 16. The exhaust silencer according to claim 14 wherein said upper shell includes an upper wall and a pair of vertical side walls extending from opposing edges of said upper wall and wherein said plurality of straps includes a first strap fixed to one of said pair of vertical side walls, a second strap fixed to another of said pair of vertical side walls, a third strap fixed to said upper wall adjacent one of said opposing edges, and a fourth strap fixed to said upper wall adjacent another of said opposing edges.
 17. The exhaust silencer according to claim 14 wherein said acoustic damping material comprises a mat that covers one portion of said inner surface of said upper shell while leaving a second portion of said inner surface of said upper shell uncovered.
 18. The exhaust silencer according to claim 17 wherein said mat is formed from a fiberglass material, and said plurality of straps and said upper shell are formed from a stainless steel material. 